java.lang.Integer

public final class java.lang

Integer

Java SE 6

Extends: Number

Implements: Comparable

The Integer class wraps a value of the primitive type int in an object. An object of type Integer contains a single field whose type is int.

In addition, this class provides several methods for converting an int to a String and a String to an int, as well as other constants and methods useful when dealing with an int.

Implementation note: The implementations of the "bit twiddling" methods (such as highestOneBit and numberOfTrailingZeros) are based on material from Henry S. Warren, Jr.'s Hacker's Delight, (Addison Wesley, 2002).

version 1.92, 04/07/06

since JDK1.0

Fields

final public static int

MIN_VALUE
A constant holding the minimum value an int can have, -2³¹.

final public static int

MAX_VALUE
A constant holding the maximum value an int can have, 2³¹-1.

final public static Class

TYPE
The Class instance representing the primitive type int.

since

JDK1.1

final public static int

SIZE
The number of bits used to represent an int value in two's complement binary form.

since

1.5

Constructors

public

Integer(int value)
Constructs a newly allocated Integer object that represents the specified int value.

value the value to be represented by the Integer object.

public

Integer(String s) throws NumberFormatException
Constructs a newly allocated Integer object that represents the int value indicated by the String parameter. The string is converted to an int value in exactly the manner used by the parseInt method for radix 10.

s	the `String` to be converted to an `Integer`.
Throws	NumberFormatException: if the `String` does not contain a parsable integer.
See also	parseInt(java.lang.String, int)

Methods

public static int

bitCount(int i)
Returns the number of one-bits in the two's complement binary representation of the specified int value. This function is sometimes referred to as the population count.

return	the number of one-bits in the two's complement binary representation of the specified `int` value.
since	1.5

public byte

byteValue()
Returns the value of this Integer as a byte.

public int

compareTo(Integer anotherInteger)
Compares two Integer objects numerically.

anotherInteger	the `Integer` to be compared.
return	the value `0` if this `Integer` is equal to the argument `Integer`; a value less than `0` if this `Integer` is numerically less than the argument `Integer`; and a value greater than `0` if this `Integer` is numerically greater than the argument `Integer` (signed comparison).
since	1.2

public static Integer

decode(String nm) throws NumberFormatException
Decodes a String into an Integer. Accepts decimal, hexadecimal, and octal numbers given by the following grammar:

DecodableString:
Sign_opt DecimalNumeral
Sign_opt 0x HexDigits
Sign_opt 0X HexDigits
Sign_opt # HexDigits
Sign_opt 0 OctalDigits

Sign:
-

DecimalNumeral, HexDigits, and OctalDigits are defined in §3.10.1 of the Java Language Specification.

The sequence of characters following an (optional) negative sign and/or radix specifier ("0x", "0X", "#", or leading zero) is parsed as by the Integer.parseInt method with the indicated radix (10, 16, or 8). This sequence of characters must represent a positive value or a NumberFormatException will be thrown. The result is negated if first character of the specified String is the minus sign. No whitespace characters are permitted in the String.

nm the String to decode.

return a Integer object holding the int value represented by nm

Throws NumberFormatException: if the String does not contain a parsable integer.

See also parseInt(java.lang.String, int)

public double

doubleValue()
Returns the value of this Integer as a double.

public boolean

equals(Object obj)
Compares this object to the specified object. The result is true if and only if the argument is not null and is an Integer object that contains the same int value as this object.

obj	the object to compare with.
return	`true` if the objects are the same; `false` otherwise.

public float

floatValue()
Returns the value of this Integer as a float.

public int

hashCode()
Returns a hash code for this Integer.

return a hash code value for this object, equal to the primitive int value represented by this Integer object.

public static int

highestOneBit(int i)
Returns an int value with at most a single one-bit, in the position of the highest-order ("leftmost") one-bit in the specified int value. Returns zero if the specified value has no one-bits in its two's complement binary representation, that is, if it is equal to zero.

return	an `int` value with a single one-bit, in the position of the highest-order one-bit in the specified value, or zero if the specified value is itself equal to zero.
since	1.5

public int

intValue()
Returns the value of this Integer as an int.

public long

longValue()
Returns the value of this Integer as a long.

public static int

lowestOneBit(int i)
Returns an int value with at most a single one-bit, in the position of the lowest-order ("rightmost") one-bit in the specified int value. Returns zero if the specified value has no one-bits in its two's complement binary representation, that is, if it is equal to zero.

return	an `int` value with a single one-bit, in the position of the lowest-order one-bit in the specified value, or zero if the specified value is itself equal to zero.
since	1.5

public static int

numberOfLeadingZeros(int i)
Returns the number of zero bits preceding the highest-order ("leftmost") one-bit in the two's complement binary representation of the specified int value. Returns 32 if the specified value has no one-bits in its two's complement representation, in other words if it is equal to zero.

Note that this method is closely related to the logarithm base 2. For all positive int values x:

floor(log₂(x)) = 31 - numberOfLeadingZeros(x)
ceil(log₂(x)) = 32 - numberOfLeadingZeros(x - 1)

return	the number of zero bits preceding the highest-order ("leftmost") one-bit in the two's complement binary representation of the specified `int` value, or 32 if the value is equal to zero.
since	1.5

public static int

numberOfTrailingZeros(int i)
Returns the number of zero bits following the lowest-order ("rightmost") one-bit in the two's complement binary representation of the specified int value. Returns 32 if the specified value has no one-bits in its two's complement representation, in other words if it is equal to zero.

return	the number of zero bits following the lowest-order ("rightmost") one-bit in the two's complement binary representation of the specified `int` value, or 32 if the value is equal to zero.
since	1.5

public static int

parseInt(String s, int radix) throws NumberFormatException
Parses the string argument as a signed integer in the radix specified by the second argument. The characters in the string must all be digits of the specified radix (as determined by whether int) returns a nonnegative value), except that the first character may be an ASCII minus sign '-' ('\u002D') to indicate a negative value. The resulting integer value is returned.

An exception of type NumberFormatException is thrown if any of the following situations occurs:

The first argument is null or is a string of length zero.
The radix is either smaller than java.lang.Character#MIN_RADIX or larger than java.lang.Character#MAX_RADIX.
Any character of the string is not a digit of the specified radix, except that the first character may be a minus sign '-' ('\u002D') provided that the string is longer than length 1.
The value represented by the string is not a value of type int.

Examples:

 parseInt("0", 10) returns 0
 parseInt("473", 10) returns 473
 parseInt("-0", 10) returns 0
 parseInt("-FF", 16) returns -255
 parseInt("1100110", 2) returns 102
 parseInt("2147483647", 10) returns 2147483647
 parseInt("-2147483648", 10) returns -2147483648
 parseInt("2147483648", 10) throws a NumberFormatException
 parseInt("99", 8) throws a NumberFormatException
 parseInt("Kona", 10) throws a NumberFormatException
 parseInt("Kona", 27) returns 411787

s	the `String` containing the integer representation to be parsed
radix	the radix to be used while parsing `s`.
return	the integer represented by the string argument in the specified radix.
Throws	NumberFormatException: if the `String` does not contain a parsable `int`.

public static int

parseInt(String s) throws NumberFormatException
Parses the string argument as a signed decimal integer. The characters in the string must all be decimal digits, except that the first character may be an ASCII minus sign '-' ('\u002D') to indicate a negative value. The resulting integer value is returned, exactly as if the argument and the radix 10 were given as arguments to the int) method.

s	a `String` containing the `int` representation to be parsed
return	the integer value represented by the argument in decimal.
Throws	NumberFormatException: if the string does not contain a parsable integer.

public static int

reverse(int i)
Returns the value obtained by reversing the order of the bits in the two's complement binary representation of the specified int value.

return	the value obtained by reversing order of the bits in the specified `int` value.
since	1.5

public static int

reverseBytes(int i)
Returns the value obtained by reversing the order of the bytes in the two's complement representation of the specified int value.

return	the value obtained by reversing the bytes in the specified `int` value.
since	1.5

public static int

rotateLeft(int i, int distance)
Returns the value obtained by rotating the two's complement binary representation of the specified int value left by the specified number of bits. (Bits shifted out of the left hand, or high-order, side reenter on the right, or low-order.)

Note that left rotation with a negative distance is equivalent to right rotation: rotateLeft(val, -distance) == rotateRight(val, distance). Note also that rotation by any multiple of 32 is a no-op, so all but the last five bits of the rotation distance can be ignored, even if the distance is negative: rotateLeft(val, distance) == rotateLeft(val, distance & 0x1F).

return the value obtained by rotating the two's complement binary representation of the specified int value left by the specified number of bits.

since 1.5

public static int

rotateRight(int i, int distance)
Returns the value obtained by rotating the two's complement binary representation of the specified int value right by the specified number of bits. (Bits shifted out of the right hand, or low-order, side reenter on the left, or high-order.)

Note that right rotation with a negative distance is equivalent to left rotation: rotateRight(val, -distance) == rotateLeft(val, distance). Note also that rotation by any multiple of 32 is a no-op, so all but the last five bits of the rotation distance can be ignored, even if the distance is negative: rotateRight(val, distance) == rotateRight(val, distance & 0x1F).

return the value obtained by rotating the two's complement binary representation of the specified int value right by the specified number of bits.

since 1.5

public short

shortValue()
Returns the value of this Integer as a short.

public static int

signum(int i)
Returns the signum function of the specified int value. (The return value is -1 if the specified value is negative; 0 if the specified value is zero; and 1 if the specified value is positive.)

return	the signum function of the specified `int` value.
since	1.5

public static String

toBinaryString(int i)
Returns a string representation of the integer argument as an unsigned integer in base 2.

The unsigned integer value is the argument plus 2³² if the argument is negative; otherwise it is equal to the argument. This value is converted to a string of ASCII digits in binary (base 2) with no extra leading 0s. If the unsigned magnitude is zero, it is represented by a single zero character '0' ('\u0030'); otherwise, the first character of the representation of the unsigned magnitude will not be the zero character. The characters '0' ('\u0030') and '1' ('\u0031') are used as binary digits.

i an integer to be converted to a string.

return the string representation of the unsigned integer value represented by the argument in binary (base 2).

since JDK1.0.2

public static String

toHexString(int i)
Returns a string representation of the integer argument as an unsigned integer in base 16.

The unsigned integer value is the argument plus 2³² if the argument is negative; otherwise, it is equal to the argument. This value is converted to a string of ASCII digits in hexadecimal (base 16) with no extra leading 0s. If the unsigned magnitude is zero, it is represented by a single zero character '0' ('\u0030'); otherwise, the first character of the representation of the unsigned magnitude will not be the zero character. The following characters are used as hexadecimal digits:

 0123456789abcdef

These are the characters '\u0030' through '\u0039' and '\u0061' through '\u0066'. If uppercase letters are desired, the java.lang.String#toUpperCase() method may be called on the result:

 Integer.toHexString(n).toUpperCase()

i	an integer to be converted to a string.
return	the string representation of the unsigned integer value represented by the argument in hexadecimal (base 16).
since	JDK1.0.2

public static String

toOctalString(int i)
Returns a string representation of the integer argument as an unsigned integer in base 8.

The unsigned integer value is the argument plus 2³² if the argument is negative; otherwise, it is equal to the argument. This value is converted to a string of ASCII digits in octal (base 8) with no extra leading 0s.

If the unsigned magnitude is zero, it is represented by a single zero character '0' ('\u0030'); otherwise, the first character of the representation of the unsigned magnitude will not be the zero character. The following characters are used as octal digits:

01234567

These are the characters '\u0030' through '\u0037'.

i	an integer to be converted to a string.
return	the string representation of the unsigned integer value represented by the argument in octal (base 8).
since	JDK1.0.2

public static String

toString(int i, int radix)
Returns a string representation of the first argument in the radix specified by the second argument.

If the radix is smaller than Character.MIN_RADIX or larger than Character.MAX_RADIX, then the radix 10 is used instead.

If the first argument is negative, the first element of the result is the ASCII minus character '-' ('\u002D'). If the first argument is not negative, no sign character appears in the result.

The remaining characters of the result represent the magnitude of the first argument. If the magnitude is zero, it is represented by a single zero character '0' ('\u0030'); otherwise, the first character of the representation of the magnitude will not be the zero character. The following ASCII characters are used as digits:

   0123456789abcdefghijklmnopqrstuvwxyz

These are '\u0030' through '\u0039' and '\u0061' through '\u007A'. If radix is N, then the first N of these characters are used as radix-N digits in the order shown. Thus, the digits for hexadecimal (radix 16) are 0123456789abcdef. If uppercase letters are desired, the java.lang.String#toUpperCase() method may be called on the result:

 Integer.toString(n, 16).toUpperCase()

i	an integer to be converted to a string.
radix	the radix to use in the string representation.
return	a string representation of the argument in the specified radix.
See also	MAX_RADIX, MIN_RADIX

public static String

toString(int i)
Returns a String object representing the specified integer. The argument is converted to signed decimal representation and returned as a string, exactly as if the argument and radix 10 were given as arguments to the int) method.

i	an integer to be converted.
return	a string representation of the argument in base 10.

public String

toString()
Returns a String object representing this Integer's value. The value is converted to signed decimal representation and returned as a string, exactly as if the integer value were given as an argument to the java.lang.Integer#toString(int) method.

return

a string representation of the value of this object in base 10.

public static Integer

valueOf(String s, int radix) throws NumberFormatException
Returns an Integer object holding the value extracted from the specified String when parsed with the radix given by the second argument. The first argument is interpreted as representing a signed integer in the radix specified by the second argument, exactly as if the arguments were given to the int) method. The result is an Integer object that represents the integer value specified by the string.

In other words, this method returns an Integer object equal to the value of:

new Integer(Integer.parseInt(s, radix))

s	the string to be parsed.
radix	the radix to be used in interpreting `s`
return	an `Integer` object holding the value represented by the string argument in the specified radix.
Throws	NumberFormatException: if the `String` does not contain a parsable `int`.

public static Integer

valueOf(String s) throws NumberFormatException
Returns an Integer object holding the value of the specified String. The argument is interpreted as representing a signed decimal integer, exactly as if the argument were given to the #parseInt(java.lang.String) method. The result is an Integer object that represents the integer value specified by the string.

In other words, this method returns an Integer object equal to the value of:

new Integer(Integer.parseInt(s))

s	the string to be parsed.
return	an `Integer` object holding the value represented by the string argument.
Throws	NumberFormatException: if the string cannot be parsed as an integer.

public static Integer

valueOf(int i)
Returns a Integer instance representing the specified int value. If a new Integer instance is not required, this method should generally be used in preference to the constructor #Integer(int), as this method is likely to yield significantly better space and time performance by caching frequently requested values.

i	an `int` value.
return	a `Integer` instance representing `i`.
since	1.5

Properties

public static Integer

getInteger(String nm)
Determines the integer value of the system property with the specified name.

The first argument is treated as the name of a system property. System properties are accessible through the java.lang.System#getProperty(java.lang.String) method. The string value of this property is then interpreted as an integer value and an Integer object representing this value is returned. Details of possible numeric formats can be found with the definition of getProperty.

If there is no property with the specified name, if the specified name is empty or null, or if the property does not have the correct numeric format, then null is returned.

In other words, this method returns an Integer object equal to the value of:

getInteger(nm, null)

nm	property name.
return	the `Integer` value of the property.
See also	getProperty(java.lang.String), getProperty(java.lang.String, java.lang.String)

public static Integer

getInteger(String nm, int val)
Determines the integer value of the system property with the specified name.

The second argument is the default value. An Integer object that represents the value of the second argument is returned if there is no property of the specified name, if the property does not have the correct numeric format, or if the specified name is empty or null.

In other words, this method returns an Integer object equal to the value of:

getInteger(nm, new Integer(val))

but in practice it may be implemented in a manner such as:

 Integer result = getInteger(nm, null);
 return (result == null) ? new Integer(val) : result;

to avoid the unnecessary allocation of an Integer object when the default value is not needed.

nm	property name.
val	default value.
return	the `Integer` value of the property.
See also	getProperty(java.lang.String), getProperty(java.lang.String, java.lang.String)

public static Integer

getInteger(String nm, Integer val)
Returns the integer value of the system property with the specified name. The first argument is treated as the name of a system property. System properties are accessible through the java.lang.System#getProperty(java.lang.String) method. The string value of this property is then interpreted as an integer value, as per the Integer.decode method, and an Integer object representing this value is returned.

If the property value begins with the two ASCII characters 0x or the ASCII character #, not followed by a minus sign, then the rest of it is parsed as a hexadecimal integer exactly as by the method int) with radix 16.
If the property value begins with the ASCII character 0 followed by another character, it is parsed as an octal integer exactly as by the method int) with radix 8.
Otherwise, the property value is parsed as a decimal integer exactly as by the method int) with radix 10.

The second argument is the default value. The default value is returned if there is no property of the specified name, if the property does not have the correct numeric format, or if the specified name is empty or null.

nm property name.

val default value.

return the Integer value of the property.

See also getProperty(java.lang.String), getProperty(java.lang.String, java.lang.String), decode

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Java SE 6